بالفيديو كيمياء للثالث الثانوي لغات الباب الثاني 2013 |Strength of oxygenated acids

كيمياء لغات - الباب الثانى | Strength of oxygenated acids




Strength of oxygenated acids


*It depends on the number of Oxygen atoms which does not bind with

Hydrogen atoms

*Oxygenated acid have the formula MOn (OH)m

M atom of an element

On atoms of Oxygen which do not bind with Hydrogen atom

m number of oxygen bind with hydrogen


Acid

MOn (OH)m Oxygen atoms which not bind with Hydrogen Strength of acid Chemical formula

Si (OH)4

ortho siliconic _____ weak acid H4SiO4

PO (OH)3

orthophosphoric 1 moderate H3PO4

SO2 (OH)2

Sulphuric 2 strong H2SO4

ClO3 (OH)

Perochloric 3 very strong HClO4


G.R.F 1-Perochloric acid HClO4 more stronger than orthophosphoric acid.

2- Perochloric acid more stronger than sulphuric acid. Exam 2012

3- HClO4 is stronger than H4SiO4 [ orthosiliconic acid]

……… ……………………………………………………………………………………………………………………………………

4- Strength of oxygenated acids increases from left to right across the period.

………………………………………………………………………….....................

7) Graduation of oxidation number in the periodic table.


* The old definition of valence: -

Number of hydrogen atoms which combines with one atom of element.

Number of hydrogen atoms that can be replaced by one atom of element.

Ex. HF H2O NH3

(Flourine is monovalent) (Oxygen is divalent) (Nitrogen is trivalent)


* The modern definition of valence: -


Number of ( unpaired ) electrons in the valence shell of an atom.

7N 1S2 , 2S2 , 2P3 Nitrogen is trivalent because

It has three unpaired electrons G.R.F.

8O 1S2 ,2S2 , 2P4 Oxygen, is divalent because

it has two unpaired electrons.

•

* Oxidation number: -

Def * It’s a number refers to the electric charges

(positive or negative) of elements in compound.

* Difference between [oxidation number and valence]

* Whose meaning is similar to valence. but the term oxidation
number is preferred than valence because it helps us to explain the
change in the electronic structure of atoms in compounds.
G.R.F.


Example Valence Oxidation no. Example Valence Oxidation no.

Na+1 1 +1 Cl-1 1 -1

Mg+2 2 +2 O-2 2 -2


Calculation’s rules of oxidation numbers



1) The oxidation number of an atom in its elemental state equals zero.

Ex. [ O2 , O3 , N2 , S , H2 , O3 , S8 , P4 , Cl2 ]

2) Sum. oxidation numbers of any compound is zero H2 S O4


3) The oxidation number of Oxygen equals –2 except that





Oxygen diflouride Hydrogen peroxide Sodium peroxide

O F2 H2O2 Na2O2


O F2 H2 O2 Na2 O2


O = +2 O = -2/2 = -1 O = -2/2 = -1


4) The oxidation number of Hydrogen (+1) except [metal hydrides]



Ca H2 NaH

Ca H2 Na H


H = -2/2 = -1 H = -1


*On electrolysis of Sodium hydrides , Hydrogen gas evolves at anode

because oxidation number of Hydrogen in hydrides = -1 G.R.F


5) In the formula for an atomic group (radical) the sum of
oxidation numbers equals the charge of the group. For example, in the
radical.

(Cr2 O7 ) , the sum of all oxidation number is = -2


Calculate oxidation number in each of the following

1- Oxygen in {OF2 , KO2 , Na2O2 , Li2O , O3 , O2 }


2- Chlorine in { NaCl , NaClO4 , NaClO3 , NaClO2 , NaClO }





3- Nitrogen in { NO2 , HNO2 , NO , N2O , N2 , NH3 , ( NO3)-1,(NO2)-1





4- Sulphur in {Na2S2O3 , K2S , SO2 , NaHSO3 , H2SO4 , (SO4)-2




5- Manganese in {KMnO4 , MnO2 , (MnO4)-1 , MnCl2 }



6- Iron in {FeSO4 , Fe2(SO4)3 , }



7- Sulphur in { ferric sulphate , ferrus sulphate }

Fe2(SO4)3 FeSO4




*Oxidation number of some elements:-

Group 1A 2A 3A

O.N +1 +2 +3

Ex Li ,Na , K , Rb , Cs Be , Mg ,Ca , Ba Al





Oxidation :-

*It is the process of losing electrons leading to increasing the positive

charges or decreasing the negative charges


Reduction :-

*It is the process of gaining electrons leading to increasing the negative

charges or decreasing the positive charges


Oxidizing agent :-

Substance which takes electron , takes hydrogen or gives oxygen


Reducing agent :-

Substance which gives electron , takes oxygen or gives hydrogen

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